According to the basic principle of dry and wet type thermometers a tests can be made using a simple sling psychrometer wherein one bulb which has been covered with moistened cloth is swung at the rate of approximately 1000 feet per minute. Since the air is made to flow past the thermometer, the temperature reading of the wet bulb will be lower than that of the dry one which is at the atmospheric temperature. The decrease in temperature is due to the evaporation of water from the moistened cloth.
Human body temperature can also be measured with the thermometer. With its natural skin human beings could feel the range of temperature changes from cold to warm through the skin. When the skin is covered with seat as a result of warm weather the body temperature could be lowered by just letting the air flow pass the skin. The evaporating sweat also draws the heat from the body.
In a conventional evaporative condensing unit or chiller, water is pumped up to a higher level before being cascaded down as fine droplets or mist. Air is then blown in an opposite direction to the water flow passing the the refrigerant fluid flowing within conduit of the heat exchanger in order to reduce the temperature of the refrigerant fluid. However, this process involves the use of a high volume of water with a not very high thermal efficiency, because, before reaching the heat exchanger, the air has already been fully saturated while being blown through the mist.